Investigating asymmetries in the HD$^{+}$(1$s\sigma )$ branching ratio following electron impact at energies from threshold to 100

We present preliminary results where momentum-imaging is used to investigate e$^{-}$ + HD collisions at energies from near threshold to 100 eV. Single ionization proceeding to the ground (1$s\sigma )$ electronic state usually results in the production of HD$^{+}$, but a small fraction of the ionization events reach the vibrational continuum, leading to H$^{+}$+D(1$s)$ or, via charge transfer to the 2$p\sigma $ state, H(1$s)$ + D$^{+}$. The H(1$s)$ + D$^{+}$ final state is 3.7 meV higher than the H$^{+}$ + D(1s) state at the separate atom limit. When initiated by fast ion impact, this energy difference leads to a measurable asymmetry in the ground state dissociation process [1]. Fast electron impact is expected to produce a similar result, but as the electron energy is reduced toward threshold, this asymmetry may increase and have significant astrophysical implications. [1] E. Wells, B.D. Esry, K.D. Carnes, and I. Ben-Itzhak, Phys. Rev. A \textbf{62}, 062707 (1999).